Solid-state lighting (SSL) is anticipated to be the next generation of efficient lighting to replace traditional incandescent or fluorescent lamps. SSL devices are primarily based on inorganic light emitting diodes (LEDs), with ongoing development in organic LEDs (OLEDs). A challenge is to improve the color quality of such devices. Currently, commercial LEDs produce white light by exciting yellow-emitting YAG:Ce phosphors with blue InGaN LEDs, resulting in bluish white light having a poor color rendering index (CRI) that is not suitable for general illumination. Higher quality devices add a red-emitting inorganic phosphor, such as Eu2+-doped nitridosilicates, to produce light that can realistically render orange and red objects; yet, they have a broad emission that extends to the near IR, producing unseen illumination. Increasing the lumens of red light per watt of light emitted (high luminous efficacy of radiation) requires strong emission at ˜615 nm, which can be achieved with Eu3+-doped phosphors. Eu3+-doped inorganic phosphors have quantum yields (QYs) as high as 88%, extremely low thermal quenching, and tremendous thermal and chemical stability. Unfortunately, they have drawbacks including high annealing temperatures (900° C. or higher) and low blue absorbance (which limits their use in SSL devices that are based on blue InGaN LED excitation).
The need remains, therefore, for a light emitting material that is energy-efficient to produce; and satisfies the criteria for applications such as solid-state lighting. The need also remains for a light emitting material that uses no or very limited rare earth elements in its composition.